Periscopes provide the user with the ability to observe their surroundings from underwater while maintaining secrecy. The construction of the periscope is fairly simple: several tubes, lenses and mirrors are put together to form the tool. Other, more complicated, versions of the periscope exist, too. These use prisms and special lenses which allow the periscope to view objects from a greater distance.
The periscope features a relatively simple design, even if more recent prism technology, which is used to reflect images, is more complicated. The basic design of a periscope is a tube accompanied by two mirrors, one at each end, parallel to one another and turned at a 45 degree angle. The positioning of these mirrors allows an image to be reflected from one end of the instrument to the other. The use of lenses and prisms allows for a sharper image and magnification.
The history of the telescope stretches back to the famous printer Johann Gutenberg, an inventor who greatly improved the printing press. In the 15th century, Gutenberg developed a proto-periscope that was used by individuals to see above others in a crowd. Later, in the 17th century, Johannes Hevelius discussed the potential military uses of this instrument, and by the early 20th century, the periscope was perfected and used in World War I to allow soldiers to see out of trenches without peering above them.
Uses in Submarines
Periscopes are perhaps best known for their use in submarines. When used in this way, periscopes are set into the top of the submarine and are equipped to turn 360 degrees so submariners can obtain a total view of the horizon without attracting attention. The periscopes equipped in submarines usually feature six times magnification and are noncorrosive so they do not corrode when used in salt water.
Uses in Tanks
Before they were used in submarines, periscopes were employed in tanks -- and still are. Periscopes allow tank operators to view, in 360 degrees, the space around them without leaving their tank. The ability to rotate the periscope on a tank 360 degrees was introduced with the Gundlach Rotary Periscope in 1936. This technology was first used in British tanks and was later transferred to the American military. Eventually the design was copied by the Soviet Union and, later still, by Germany.